“Men are weak. Our duty as gods is to make them strong. Our hands must be firm.”
—Duma to Mila in Echoes: Shadows of Valentia
Duma is the patron deity of Rigel who is worshiped as the War Father (戦神, Ikusagami lit. God of War), but, by the events of the game, he has been denounced as a Fell God (邪神, Jashin lit. Evil God) by some of the characters because of his descent into madness. Thousands of years ago, Duma was exiled from Archanea to Valentia by Naga after a dispute he had with her, with Mila following him into exile as well. Duma was also given Falchion by Naga to be used to end his and Mila's life in the event the two Divine Dragons fall to madness. In Valentia's early days, he came into violent dispute with his sister Mila over their beliefs: Duma believing mankind should strive for power and Mila believing that mankind should be led towards peace and pleasure. Eventually, the two came to a pact that divided the continent between them, the north to Duma and the south to Mila, although their heavy involvement led to the people of Rigel becoming too cruel and the people of Zofia becoming hedonistic.
Thousands of years later, Duma supplies Rigel's emperor, Rudolf, with the Falchion in order to seal Mila, during which it is revealed that Duma has slowly descended into madness. During the war, Duma's head priest Jedah tries to figure what troubles Duma, and comes to a conclusion that he needs Celica's soul to ease his pain. Duma would telepathically make attempts to contact Berkut serval times during the war, offering him power. Berkut eventually does by sacrificing Rinea after learning the truth about Alm's true heritage. Duma's priest Jedah eventually succeeds in his goal of sacrificing Celica's soul to Duma after tricking her into believing he can free Mila from stone. However Alm claims Falchion, saves Celica, and heads over with his army to reunite with Celica's army to face Duma and free him from his madness. After his defeat, Duma entrusts the fate of Valentia to Alm, and then falls into a great slumber alongside Mila. Duma and Mila's faiths are merged into one religion under Nomah afterwards, and Duma's sleeping body is moved to a mountain relatively nearby Mila's.
In Fire Emblem Awakening, a location known as the Demon's Ingle, presumably where Duma is resting, appears as the location where Yen'fay is fought by Chrom and his army. While the Valm general Pheros refers to worshiping Naga and Mila, there is no mention of Duma, despite his religion being merged with Mila's at the end of Gaiden, implying he's largely been forgotten by that period. Say'ri mentions a "wicked fire god" that apparently inhabits the Demon's Ingle, this indicates the unification of the religions eventually fell apart.
It should be noted that he cannot be defeated without the use of the Falchion wielded by Alm. Duma will not take damage past 52 HP with other weapons. However, Nosferatu will still be able to do damage, due to an oversight in the coding caused by the weapon's hard-wired 50% hit rate.
It should be also noted that the final map in Gaiden is one of the few maps where Upheaval occurs, activated by Duma.
“Only power holds meaning. Only strength holds sway. Call to me. Thirst for me. Thirst for power!”
—Duma's battle quote in Echoes
“Spirits of the earth...heed my call!”
—Duma casting Upheaval in Echoes
“Where...did mankind...find...such power...?”
—Duma's defeat voice clip in Echoes
“That should be enough... Hero Alm. I entrust everything to you. Inherit the will of us siblings and govern this land... Carrying both the strength of Duma as well as the love of Mila, guide the people justly... You must not repeat the same mistakes we committed. You must never again disturb our slumber...”
—Duma's defeat quote in Gaiden
“So be it, Alm. I leave Valentia's future to you, her hero. Take from us what lessons you will and shape her into a land to remember. Make her strong like Duma, and fill her with Mila's love. Let our grave mistakes be warnings of where not to tread as you lead her forth. Now, we shall sleep. And never shall you disturb our slumber.”
—Duma's defeat quote in Echoes
- Duma is one of the several final bosses in the series with the ability to move around their exclusive maps. The others are Idunn, Fomortiis, Ashnard, and Garon.
- Duma has the second highest HP total of any enemy in the series at 200 HP, losing only to Anankos. However, Duma has all of his HP in a single unit, while Anankos splits his HP between multiple parts.
- There is a unique animation if Alm (in Hero class in Echoes: Shadows of Valentia) attacks or defeats Duma with a sword. When attacking Duma, Alm will jump up and slash Duma's eye instead of his usual animation. For the final blow, Alm will attack before Duma fully rises, throwing away his shield, jumping and stabbing Duma's eye.
- Though normally Duma can only be defeated by Alm's Falchion and Nosferatu, he can also be defeated by the amiibo version of Alm if the Alm data saved to it has Falchion.
- Duma can also be defeated by an amiibo of Marth or Roy.
- In Fire Emblem Echoes: Shadows of Valentia, Mila and Duma are stated to be exiled Divine Dragons. However, it is not explained how Duma came to have tentacles and a single, laser shooting eye embedded in his forehead. Duma's decaying features are thus far unique to him and Draco Zombies.
- This makes Duma the only named dragon in the series to not use Breath to attack.
- Oddly the spells casted by Duma are mainly of the Darkness and the Earth element, unusual for a Divine Dragon.
- Duma's humanoid form in Echoes appears to be based on the mysterious figure seen in the background of Gaiden's boxart. This is supported by the fact that the Duma's Helm accessory also seems to be based on the headgear of the aforementioned figure.